Section 20.02.01.040 - ROAD CONSTRUCTION, RECONSTRUCTION AND MAINTENANCE01.Purpose. Provide standards and guidelines for road construction, reconstruction, and maintenance that will maintain forest productivity, water quality, and fish and wildlife habitat.02.Road Specifications and Plans. Road specifications and plans must be consistent with good safety practices. Landowners and Operators should plan each road to the minimum use standards adapted to the terrain and soil materials to minimize disturbances and damage to forest productivity, water quality, fish, and wildlife habitat. In addition, landowners and operators must:a. Plan transportation networks to avoid road construction within SPZs, except at approaches to stream crossings. Leave or reestablish areas of vegetation between roads and streams.b. Plan roads no wider than necessary to safely accommodate the anticipated use. Minimize cut and fill volumes by aligning the road to fit the natural terrain features as closely as possible. Adequately compact fill material. Dispose of excess material on geologically stable sites.c. Plan roads to drain naturally by out-sloping or in-sloping with cross-drainage and by grade changes where possible. Install dips, water bars, cross-drainage, or subsurface drainage on roads when necessary.d. When natural drainage will not protect the surface, cut slopes or fill slopes, plan roads with relief culverts and roadside ditches. Install culverts to prevent erosion of the fill by properly sizing, bedding and compacting. Ensure drainage structures avoid direct discharge of sediment into streams.e. This rule applies to new culvert installations, or reinstallations during road reconstructions or because of catastrophic events. Temporary culvert crossings are exempt from the fifty (50) year peak flow design requirement but must be removed before seasonal run-off. i. Culverts in fish-bearing streams must provide for fish passage.ii. Design stream crossings to carry the fifty (50) year peak flow using Department accepted engineering methods or the culvert sizing table below. Armor the inlet or use a flared inlet structure on thirty (30) inch or greater diameter culverts. The minimum diameter culvert allowed is eighteen (18) inches. CULVERT SIZING TABLE
The left side of this culvert sizing table will be used for the area of the state north of the Salmon River and within the South Fork Salmon River drainage; the right side will be used for the area of the state south of the Salmon River and outside the South Fork Salmon River drainage. It was developed to carry the fifty (50) year peak flow at a headwater-to-diameter ratio of one (1).
North Forest Region and South Fork Salmon River Drainage | | South Forest Region |
Watershed Area (acres) | Required Culvert Diameter (inches) | Culvert Capacity (in cubic feet/sec) | Watershed Area (acres) |
Ditch relief, seeps, springs, wet areas, draws | 12 | NA | Ditch relief, seeps, springs, wet areas, draws |
less than 32 | 18 | 6 | Less than 72 |
33 - 74 | 24 | 12 | 73-150 |
75 - 141 | 30 | 20 | 151-270 |
142 - 240 | 36 | 32 | 271-460 |
241 - 366 | 42 | 46 | 461-720 |
367 - 546 | 48 | 65 | 471-1025 |
547 - 787 | 54 | 89 | 1026-1450 |
788 - 1027 | 60 | 112 | 1451-1870 |
1028 - 1354 | 66 | 142 | 1871-2415 |
1355 - 1736 | 72 | 176 | 2416-3355 |
1737 - 2731 | 84 | 260 | 3356-5335 |
2732 - 4111 | 96 | 370 | 5336-7410 |
4112 - 5830 | 108 | 500 | 7411-9565 |
5831 - 8256 | 120 | 675 | 9566-11780 |
Culverts larger than one hundred twenty (120) inches must be designed; consider alternative structures.
iii. Relief culverts, and those used for seeps, springs, wet areas, and draws must not be less than twelve (12) inches in diameter for permanent installations.f. On existing roads that are not reconstructed or damaged by catastrophic events, landowners or operators are encouraged, but not required, to replace or provide mitigation for culverts that do not provide for fish passage in accordance with Subparagraph 040.02.e.i. or cannot carry the fifty (50) year peak flow of Subparagraph 040.02.e.ii.g. Plan and install stream crossings in compliance with the Stream Channel Protection Act (Title 42, Chapter 38, Idaho Code), Paragraph 030.07.b. and the culvert sizing requirements of Paragraph 040.02.e. Fords are acceptable stream crossing structures on small, shallow streams, with gradients less than four percent (4%). For fords: cross-drain and rock the road surface on each side of the stream for at least seventy-five (75) feet for Class I and at least thirty (30) feet for Class II streams; minimize sediment delivery to streams by limiting use to low water, dry, or frozen conditions; minimize hauling or equipment crossing trips during times of salmonid spawning and egg incubation.h. Avoid reconstruction of existing roads located in SPZs, except for approaches to stream crossings, unless it will result in the least long-term impact on site productivity, water quality, and fish and wildlife habitat. Reconstruction of existing roads in SPZs requires a variance. Reusing existing roads in SPZs for skidding or landing logs requires a variance. Reusing existing roads in SPZs only for hauling fully suspended logs does not require a variance.03.Road Construction. Landowners and operators must use the following practices to construct or reconstruct roads in a way that prevents debris, overburden, and other material from entering streams.a. Construct roads in compliance with the planning guidelines of Subsection 040.02.b. Clear all debris generated during construction or maintenance which potentially interferes with drainage or water quality. Deposit excess material and slash on geologically stable sites outside the SPZs.c. Where sediments would enter streams, stabilize exposed material (road surface, cut slopes, fill slopes, borrow pits, waste piles, etc.) prior to seasonal runoff. Install supplemental stabilization measures such as seed and mulch, slash mats, or rock. Rock the road surface through the entire SPZ over Class I stream crossings.d. Compact road fills. Minimize snow, ice, or frozen soil buried in embankments. Significant woody material is not allowed in fills, but slash may be used as a filter windrow along the fill toe in compliance with the Idaho Forestry Act and Fire Hazard Reduction Programs, Title 38, Chapters 1 and 4, Idaho Code.e. During and following operations on out-sloped roads, retain out-slope drainage and remove berms on the outside edge, except those intentionally constructed for road grade fill protection.f. Provide for drainage of quarries to prevent sediment from entering streams.g. Construct cross-drains and relief culverts to minimize erosion. Use riprap, vegetative matter, downspouts, and similar devices to minimize erosion of the fill. Install drainage structures or cross-drain incomplete roads prior to seasonal runoff. If effective forest floor filtration is not available within SPZs, install supplemental filtration at drainage structure outlets or additional drainage structures outside SPZs to prevent road surface erosion from entering streams.h. Postpone earthwork or material hauling during wet periods if erodible material would enter streams.i. Remove or stabilize cut-slope material subject to sloughing concurrent with construction.j. Construct full-bench roads, without fill slope disposal on slopes greater than sixty percent (60%) in unstable or erodible soils.04.Road Maintenance. Landowners and operators must use the following practices for regular preventive maintenance operations to minimize disturbance and damage to forest productivity, water quality, and fish and wildlife habitat.a. Place all debris or slide material associated with road maintenance in a manner to prevent their entry into streams.b. Repair slumps, slides, and other erosion sources causing stream sedimentation to minimize sediment delivery.c. Active forest roads are used for hauling forest products, rock and other road building materials. Conduct the following maintenance on active roads. i. Keep culverts and ditches functional.ii. Crown, out-slope, in-slope, or cross-drain road surfaces during and upon completion of seasonal operations. Remove berms from the outside edge except those intentionally constructed for protection of fills.iii. Maintain the road surface and postpone hauling during wet periods as necessary to minimize erosion of the subgrade and provide proper drainage.iv. Apply road-surface stabilizing materials in a way that prevents their entry into streams.v. During active maintenance, ensure road surfaces within SPZs are sufficiently stabilized. Install supplemental filtration at drainage structure outlets within SPZs if effective forest floor filtration is not available.d. Incidental haul roads are roads with a primary purpose other than forest practices that are used for hauling logs during active harvest. Active road maintenance requirements apply. Once active road maintenance is completed, no other maintenance is required under the Act.e. Inactive forest roads are no longer used for commercial hauling, but maintained for access. Conduct the following maintenance on inactive roads.i. When active use is over, clear ditches and culverts, crown, out-slope, in-slope, cross-drain or otherwise treat the road surface to minimize erosion. Maintain drainage structures as needed.ii. The roads may be permanently or seasonally blocked to vehicle traffic.f. Long-term inactive roads are forest roads that will not be used soon, but may be used again; no subsequent maintenance is required following completion of the practices below: i. Out-slope, cross-drain, seed or treat the surface to control erosion.ii. Block the road to vehicle traffic.iii. The Department may require the removal of bridges, culverts, ditches and unstable fills. The landowner must maintain any bridges or culverts left in place.g. Permanently abandoned roads are forest roads not intended to be used again. Remove all drainage structures and treat road surfaces to minimize erosion.i. Restore stream gradients to their natural slope.ii. Treat the road surface to break up compacted areas.iii. Pull back fill slopes of roads within SPZs to a stable configuration unless long-term stability is evident.iv. Pull back unstable side-hill fills to a stable configuration.v. Control ditch-line erosion by cross-draining, out-sloping, or regrading to eliminate ditches.vi. Stabilize soil exposed from regrading, ripping, and drainage removal by seeding, mulching, armoring, or other treatment.05.Winter Operations. To minimize erosion and prevent damage to roads and constructed skid trails from winter logging, operators must implement the practices below: a. Install adequate road drainage prior to winter operations using rolling dips, drivable cross-drains, open-top culverts, out slopes, or other methods.b. Maintain roads to keep the surface drained during thaws or break up. This may require active maintenance of existing drainage, drain holes in snow berms, and installation of additional cross-drains or treatment of the road surface.Idaho Admin. Code r. 20.02.01.040